UNIVERSITY   OF   CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL   EXPERIMENT   STATION 

BERKELEY,  CALIFORNIA 


APPLE   POLLINATION   STUDIES 
IN  CALIFORNIA 


E.  L.  OVERHOLSER 


BULLETIN  426 

May,  1927 


UNIVERSITY  OF  CALIFORNIA  PRINTING  OFFICE 

BERKELEY,  CALIFORNIA 

1927 


APPLE  POLLINATION  STUDIES  IN  CALIFORNIA 

E.  L.  OVEBHOLSERi 

Pollination  requirements  of  apple  varieties  have  received  much 
attention  from  a  number  of  workers  in  the  United  States.  Among 
those  who  have  studied  the  problem  are  Waugh  (1898),  Waite  (1899), 
Powell  (1902),  Lewis  and  Vincent  (1909),  Wicks  (1918),  Gowan 
(1920),  Vincent  (1920),  Morris  (1921),  Auchter  (1922),  Crandall 
(1922),  and  MacDaniels  (1926).  Because  of  the  fact  that  their 
reports  are  not  always  in  agreement,  that  the  pollination  requirements 
of  individual  varieties  may  differ  in  the  several  sections  of  the  country, 
(Tufts  and  Philp,  1923),  and  that  several  varieties  grown  in  California 
have  not  previously  received  much  attention,  the  studies  recorded  in 
this  paper  were  undertaken. 

The  Yellow  Newtown  and  the  Yellow  Bellflower,  both  in  the  Pajaro 
Valley,  and  the  Gravenstein  in  the  Sebastopol  section  are  the  principal 
varieties  grown  in  California.  While  the  Yellow  Bellflower  and 
Gravenstein  generally  bloom  profusely,  they  sometimes  fail  to  develop 
commercial  crops.  On  the  other  hand,  even  when  planted  in  separate 
blocks,  they  frequently  set  fair  crops  of  fruit. 

In  the  coastal  counties  of  California  where  the  studies  were 
conducted,  the  blooming  period  of  apples  is  relatively  long,  being 
sometimes  six  or  eight  weeks  in  duration.  In  the  Mississippi  Valley 
and  the  Northeast,  it  lasts  only  eight  to  ten  days.  Furthermore,  under 
California  weather  conditions,  insect  activity  is  more  likely  to  prevail 
during  much  of  the  blooming  period.  It  appears,  therefore,  that  in 
normal  seasons,  lack  of  proper  varieties  for  cross-pollination  is  less 
serious  in  the  coastal  districts  of  California. 

OBJECTS  OF  THE  INVESTIGATION 

Beginning  in  1919,  pollination  studies  were  conducted  over  a  period 
of  four  years  in  the  vicinities  of  Watsonville  and  Sebastopol.2  The 
object  was  chiefly  to  determine  the  pollination  requirements  of  the 
Yellow  Newtown,  Yellow  Bellflower,  and  Gravenstein ;  and  incidentally 
to  find  out  the  part  played  by  bees  in  effecting  pollination,  the  relative 
time  of  blooming,  and  the  abundance  and  the  viability  of  the  pollen 


i  Assistant  Professor  of  Pomology  and  Associate  Pomologist  in  the  Experiment 
Station. 

2  The  writer  is  under  obligation  to  Mr.  C.  J.  Eodgers  of  Watsonville  and  to 
Mr.  Wm.  Hotle  and  Mr.  Henry  Elphick  of  the  Sebastopol  district  for  the  use 
of  their  orchards,  and  to  the  Sonoma  County  Farm  Advisors  for  their  cooperation. 


4  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION 

produced.  Attempts  were  made  to  discover  satisfactory  pollinizers 
for  the  three  varieties  mentioned  and,  in  turn,  the  varieties  that  would 
pollinate  them.  In  order  to  determine  whether  the  results  obtained 
from  the  experimental  work  were  in  agreement  with  the  experience 
of  growers,  observations  covering  a  period  of  two  years  were  made  in 
a  number  of  orchards  throughout  the  county  where  these  varieties 
were  available.  Without  exception  the  data  obtained  in  the  experi- 
ments were  found  to  be  in  agreement  with  field  experience. 

All  the  trees  utilized  were  in  a  healthy,  well  kept  condition.  The 
age  of  those  at  Watsonville  was  about  20  years,  of  those  at  Sebastopol, 
from  10  to  25  years.  At  Sebastopol  the  varieties  employed  were  the 
Gravenstein,  Delicious,  Jonathan,  Esopus  (Spitzenburg),  Baldwin, 
Tompkins  King,  Yellow  Bellflower,  and  Rhode  Island  Greening;  at 
Watsonville,  the  Yellow  Newtown,  Yellow  Bellflower,  White  Winter 
Pearmain,  and  Red  Pearmain. 

In  the  study  of  the  actual  transfer  of  pollen  thousands  of  hand 
pollinations  were  made.  The  results  were  then  compared  with  the 
work  of  bees.  Since  the  latter  play  such  an  important  part  in  trans- 
porting pollen,  it  seems  best  to  discuss  this  phase  of  the  subject  first. 

The  Use  of  Bees  in  Pollination. — The  blossom  of  the  apple,  like  that 
of  most  commercial  deciduous  fruits,  is  entomophilous,  and  supposedly 
requires  insects,  principally  bees,  for  pollen  transmission  and  pollina- 
tion. Waugh  (1898)  and  Lewis  and  Vincent  (1909),  by  using  micro- 
scope slides  coated  with  vaseline  and  glycerine  placed  in  the  orchard, 
found  that  wind-carried  pollen  was  inadequate  for  cross-pollination. 
Lewis  and  Vincent  found  that  when  1500  blossoms  on  a  seven-year-old 
apple  tree  were  emasculated,  only  5  fruits  set.  Apparently,  no  pollen 
was  carried  by  wind  from  a  profusely  blooming  tree  twenty  feet  away. 
Moreover,  no  insects  were  attracted,  because  only  the  stigmas  of  the 
flowers  remained. 

Hendrickson  (1916)  found  that  insects  may  be  necessary  for  the 
application  of  pollen  with  even  self-fruitful  varieties  of  plums,  and 
Alderman  (1918)  found  that  placing  of  bees  in  an  orchard  increased 
the  percentage  of  apple  flowers  setting  fruit.  More  recently,  Auchter 
(1922)  found  this  to  be  true  with  apples  in  Maryland. 

Following  Hendrickson 's  method,  tents  made  of  light  redwood  and 
mosquito-bar  were  used  to  restrict  bees  to  definite  trees.  The  first  and 
largest  tent  enclosed  two  trees,  one  a  Yellow  Newtown  and  the  other 
a  Yellow  Bellflower.  The  second  and  third,  which  were  small,  were 
set  over  individual  trees  of  each  of  these  varieties.  Under  each  tent 
was  placed  a  hive  of  bees.  Care  was  taken  to  leave  no  openings  through 
which  the  insects  might  pass. 


Bul.  426] 


APPLE   POLLINATION   STUDIES   IN    CALIFORNIA 


As  checks,  selected  limbs  of  other  trees  of  the  two  varieties  were 
covered  with  mosquito-bar  netting  to  exclude  all  insects.  The  remain- 
ing limbs  upon  the  trees  so  utilized  were  left  exposed  and  untreated. 

The  percentage  of  set  of  fruit  on  the  trees  and  branches  enclosed  by 
mosquito-bar  was  determined  by  counting  the  total  number  of  blossoms 
upon  certain  branches  and  recording  the  number  of  flowers  on  tags 
attached  to  each  branch.  Approximately,  two  months  later,  or  after 
a  set  of  fruit  should  have  resulted,  recounts  were  made  and  the  per- 
centage of  set  determined.  For  purposes  of  comparison,  the  percentage 
of  natural  set  on  untreated  trees  was  obtained.  The  latter  will  be 
referred  to  hereafter  as  the  "normal  set."  In  most  cases,  approxi- 
mately 5000  blossoms  representing  the  total  number  on  selected 
branches  of  six  representative  trees  distributed  throughout  the  orchard 
were  counted  each  year.  Later  when  they  had  developed,  the  fruits 
also  were  counted. 


EXPERIMENTAL   DATA  WITH    BEES 

The  first  test  of  the  value  of  bees  in  effecting  cross-pollination  in 
an  apple  orchard  was  made  in  the  spring  of  1919,  at  a  time  when  the 
trees  had  a  rather  light  bloom. 

The  various  treatments  and  tests  showing  the  relation  between 
bees  and  pollination  are  shown  in  table  1. 

TABLE  1 

Pollination  Eequirements  of  the  Yellow  Newtown  and  Yellow 

Bellflower  Apple  Trees  and  the  Value  of  Bees  as 

Carriers  of  Pollen 


Variety  and  pollination  treatment 

Number  of 
blossoms 
counted 

Number  of 
apples  set 

Per  cent 
set 

Newtown  cross-pollinated  by  Bellflower 

1794 
2046 
1768 
1018 
2709 
2531 
958 
481 

918 

381 

5 

305 

108 

39 

3 

77 

51.50 

(Under  tent  with  bees.) 
Newtown  self-pollinated 

18.62 

(Under  tent  with  bees.) 
Newtown  wind-pollinated 

0.28 

(Branches  covered  to  exclude  insects.) 
Newtown-normal  set 

29.96 

(Naturally  pollinated  by  insects.) 
Bellflower  cross-pollinated  by  Newtown 

4.31 

(Under  tent  with  bees.) 
Bellflower  self -pollinated 

1.53 

(Under  tent  with  bees.) 
Bellflower  wind-pollinated 

0.31 

(Branches  covered  to  exclude  insects.) 
Bellflower-normal  set 

16.00 

(Naturally  pollinated  by  insects.) 

6  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

The  table  yields  the  following  information: 

Bees  play  a  prominent  part  in  apple  pollination. 

The  Yellow  Bellflower  does  not  set  fruit  well  with  its  own  pollen, 
even  when  bees  are  present  in  abundance. 

The  Yellow  Newtown  is  fairly  self -fertile  but  sets  a  much  better 
crop  when  cross-pollinated  by  Yellow  Bellflower. 

Both  the  Yellow  Newtown  and  Yellow  Bellflower  apparently  set 
crops  when  the  two  are  grown  near  each  other  in  the  orchard,  provided 
insects  (preferably  bees)  are  present  as  pollen  carriers.  The  conclu- 
sion seems  justified  that  wind  pollination  is  unreliable. 

The  Yellow  Newtown  and  Yellow  Bellflower  seem  to  be  able  to 
pollinate  each  other  if  bees  are  present. 

While  the  set  of  the  tented  Yellow  Bellflower  was  increased  when 
cross-pollinated  with  Yellow  Newtown  through  the  aid  of  bees,  the  set 
was  only  slightly  over  4  per  cent  as  contrasted  with  the  normal  set  of 
16.0  per  cent  resulting  from  open  pollination  in  the  orchard.  This  indi- 
cates that  while  the  Yellow  Bellflower  pollinates  the  Yellow  Newtown, 
the  Yellow  Newtown  does  not  readily  pollinate  the  Yellow  Bellflower. 
In  this  connection,  Hooper  (1913)  obtained  evidence  indicating  that, 
while  Bramley  pistils  and  Cox  Orange  pollen  were  cross-compatible, 
Cox  Orange  pistils  and  Bramley  pollen  were  cross-incompatible. 

To  investigate  further  the  failure  to  set  fruit  when  insects  were 
excluded,  another  test  was  made  in  1920.  In  1919,  the  flowers  from 
which  insects  were  excluded  were  upon  branches  covered  by  mosquito- 
bar,  while  the  rest  of  the  tree  was  exposed  to  the  visits  of  insects  and 
hence  could  be  cross-pollinated.  Ewert  (1906,  1907,  1909)  appeared 
to  find  that  parthenocarpic  fruit,  that  is,  fruit  which  forms  without 
pollination,  is  at  a  disadvantage  on  the  tree  in  competition  with  fruits 
containing  developing  seeds  that  result  from  cross-pollination.  It 
was,  therefore,  considered  that  failure  to  set  fruit  on  the  branches 
from  which  insects  were  excluded  might  have  resulted  from  this 
unfavorable  competition.  In  the  second  test  (1920),  single  entire 
trees  of  the  Yellow  Newtown  and  the  Yellow  Bellflower  were  separately 
covered  with  mosquito-bar  tents  to  exclude  insects.  In  addition,  2371 
blossoms  of  Yellow  Newtown  and  2418  blossoms  of  Yellow  Bellflower 
on  ten  trees  of  each  variety,  chosen  at  random,  were  covered  with 
No.  10  Manila  bags  just  before  the  petals  had  expanded  sufficiently 
to  expose  the  pistils  and  stamens.  Occasional  flowers,  which  were  so 
far  advanced  as  to  expose  the  pistils  and  stamens,  were  removed. 
After  the  petals  had  fallen,  the  paper  bags  were  removed.  Not  a 
single  fruit  set  either  under  the  tents  or  in  the  bags,  notwithstanding 
the  fact  that  the  Yellow  Newtown  is  self-fruitful.    These  data  definitely 


BUL.  426]  APPLE   POLLINATION   STUDIES   IN    CALIFORNIA  7 

indicate  that  these  varieties  of  apples  under  the  conditions  of  the 
experiment  did  not  set  fruit  except  when  the  pollen  was  actually 
applied  to  the  pistils  by  insects  or  by  hand.  This  work  is  not  in  agree- 
ment with  that  of  Auchter  (1922)  who  found  that  no  greater  per- 
centage of  fruit  set  when  pollen  was  applied  with  a  brush  than  when 
bagged  blossoms  were  unmolested. 

Hand  Pollinations. — To  prevent  possible  chance  pollination  of  the 
stigmatic  surfaces  with  pollen  of  the  same  flower,  the  blossoms  employed 
for  the  hand  pollination  experiments  were  emasculated  after  the 
flowers  had  expanded  appreciably,  but  before  the  overlapping  petals 
had  parted  or  the  stigmatic  surfaces  had  become  exposed  and  before 
the  anthers  had  ruptured. 

The  emasculation,  it  was  found,  could  be  most  expeditiously  con- 
ducted by  using  the  nails  of  the  thumb  and  second  finger  to  cut 
through  the  floral  envelope,  and  then  removing  the  stamens  together 
with  the  petals  and  a  part  of  the  calyx-lobes,  only  the  pistils  being 
left.  All  flowers  too  far  advanced  or  too  immature  or  weak  in  their 
development  were  removed.  This  method  with  apples  enabled  a  single 
worker  to  make  from  1500  to  2000  emasculations  daily  and  was  more 
rapid  than  the  use  of  scissors  or  forceps.  The  emasculated  flowers 
were  immediately  covered  by  No.  10  Manila  paper  sacks,  and  the  date 
and  number  of  emasculated  flowers  recorded  on  a  tag  affixed  to  the 
bag  and  on  record  sheets. 

With  the  Yellow  Newtown,  Yellow  Bellflower,  and  Gravenstein 
varieties,  from  20  to  25  trees  in  one  to  three  orchards  were  used  for 
each  season 's  pollination  work.  With  most  of  the  other  varieties,  from 
5  to  10  trees  were  used  each  season. 

The  flower  clusters  emasculated  were  on  reasonably  vigorous  spurs, 
where  it  was  expected  conditions  would  be  favorable  for  a  reasonable 
percentage  of  flowers  to  set  fruit.  Between  the  time  of  emasculation 
and  pollination,  there  was  always  some  loss  in  the  number  of  flowers, 
due  to  undetected  injury  during  emasculation,  or  to  some  mechanical 
injury  after  emasculation.  Such  flowers  were  discarded  at  the  time 
of  pollination.  The  extent  of  this  injury  is  evidenced  by  the  fact  that 
out  of  some  72,800  flowers  emasculated,  about  62,000  were  in  satisfac- 
tory condition  for  pollination,  the  loss  being  about  12  per  cent. 

Ewert  (1907)  states  that  the  use  of  sacks  in  this  manner  subjects 
the  enclosed  spurs  or  portion  of  branch  to  unnatural  conditions  which 
may  not  be  favorable  for  the  setting  of  fruit.  Heinicke  (1917)  found 
a  larger  percentage  of  Baldwin  blossoms  set  fruit  in  translucent  than 
in  opaque  sacks.    He  attributed  this  to  the  fact  that  the  diffuse  light 


8  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

in  the  translucent  sacks  permitted  some  photo-synthetic  activiy,  while 
nearly  all  light  was  excluded  from  the  opaque  sacks.  Heinicke,  how- 
ever, in  this  experiment  was  troubled  with  aphid  injury.  The  fact  that 
aphids  frequently  cause  apples  to  adhere  which  otherwise  would  abscise 
may  have  affected  the  results.  Furthermore,  the  spurs  were  sacked 
in  the  spring  before  the  clusters  of  flowers  had  separated  and  were  not 
removed  until  late  summer.  In  the  pollination  work,  a  week  to  ten 
days  was  generally  the  maximum  period  of  time  during  which  the 
blossoms  and  fruit  remained  bagged.  Alderman  (1918)  and  Vincent 
(1920)  found  little  difference  in  the  percentage  of  flowers  which  set 
in  bags  and  on  trees  under  frames  covered  with  thin  cloth. 

Since  insects  appeared  necessary  to  effect  pollination  of  apples, 
and  since  Lewis  and  Vincent  (1909)  found  that  insects  did  not  visit 
emasculated  flowers,  it  was  felt,  in  view  of  the  opinions  of  Ewert  and 
Heinicke,  that  to  emasculate  flowers  and,  after  tagging  the  spurs  and 
branches,  to  leave  them  exposed  without  covering  with  the  paper 
sacks,  would  be  of  interest.  When  the  emasculated  and  exposed  pistils 
became  receptive,  the  pollen  was  applied  by  hand,  and  the  percentage 
of  set  compared  with  that  from  blossoms  similarly  treated  but  enclosed 
in  the  paper  sacks. 

After  the  work  in  1920  and  a  second  season's  work  in  1921,  with 
an  approximate  total  of  4000  emasculated,  non-sacked  blossoms  of  the 
Yellow  Newtown  and  4200  of  the  Yellow  Bellflower,  the  non-sacking 
method  was,  under  the  conditions  existing  and  the  varieties  tested, 
considered  unsatisfactory. 

Apparently,  the  emasculated  blossoms  dried  out  rapidly  as  a  result 
of  the  wounded  surfaces  when  not  covered  with  sacks.  The  sacked 
blossoms  did  not  dry  out  and  their  wounds  healed  readily.  Further- 
more, the  blossoms  which  did  not  fall  from  excessive  drying,  seemed 
to  have  a  shorter  and  less  definite  period,  wThen  the  stigmatic  surfaces 
indicated  a  receptive  condition  of  the  pistils.  Sax  (1922),  on  the 
other  hand,  seemed  to  find  consistent  results  with  uncovered,  emas- 
culated apple  flowers  in  Maine,  and  apparently  considered  the  method 
satisfactory. 

Collection  of  Pollen. — A  supply  of  pollen  was  obtained  by  collect- 
ing the  advanced  but  as  yet  unopened  flowers  of  each  variety  a  day 
or  so  before  the  dried  pollen  was  needed.  The  unopened  anthers 
were  removed  with  forceps  from  the  rest  of  the  floral  parts  and 
deposited  in  Petri  dishes  with  the  lids  partially  raised  so  as  to  permit 
aeration  and  slight  air  circulation  to  aid  in  the  drying.  The  anthers 
were  dried  in  reduced  sunlight,  or  occasionally  during  cloudy  weather, 


BUL.  426]  APPLE   POLLINATION   STUDIES   IN    CALIFORNIA  9 

in  an  incubator  at  a  temperature  of  27°  to  30°  C.  When  dry  the 
anthers  and  any  escaped  pollen  were  placed  in  small  glass  vials  which 
were  loosely  plugged  with  cotton  and  were  kept  in  a  dry  place  until 
ready  for  use. 

Application  of  Pollen  to  Pistils.  The  flowers  were  hand-pollinated 
from  one  to  three  days  after  emasculation.  The  stigmas  were  found 
to  be  in  a  receptive  condition  after  this  interval  of  time.  While  the 
common  practice  in  dusting  the  stigmas  with  pollen  is  to  use  a  camel 's 
hair  brush,  it  was  found  more  satisfactory  in  this  case  to  use  the 
end  of  a  cork  stopper  to  which  the  pollen  adhered  as  a  fine  coating 
of  yellow  powder.  Occasionally  the  anthers  had  to  be  broken  up  with 
a  pencil  and  the  vial  shaken. 

At  the  time  of  pollination,  a  count  of  the  blossoms  actually 
pollinated  was  made  and  the  number  noted  on  the  tags  and  record 
sheets.  The  sacks  were  again  placed  over  the  clusters.  When  the 
fruits  were  sufficiently  advanced  to  indicate  that  development  would 
continue,  the  sacks  were  permanently  removed  and  the  number  of  the 
young  fruits  recorded.  This  count  of  apples  was  compared  with  the 
number  of  blossoms  originally  pollinated  and  the  percentage  of  set 
thus  determined.  The  percentage  of  set  resulting  from  hand-pollina- 
tions was  always  compared  with  the  "normal  set"  from  flowers 
untreated  and  exposed  to  orchard  conditions  and  the  visits  of  insects. 

The  viability  of  each  lot  of  pollen  employed  in  the  hand-pollinations 
was  determined  by  germination  tests  in  10  to  12  per  cent  cane  sugar 
solutions  for  from  24  to  36  hours  at  room  temperature. 

EXPERIMENTAL    DATA    WITH    HAND-POLLINATIONS 

In  the  presentation  of  the  data,  each  of  the  more  important  varie- 
ties and  crosses  made  are  given  in  separate  tables,  and  the  data 
discussed  under  the  variety  heading. 

Yellow  Newtoivn. — The  data  obtained  with  the  Yellow  Newtown 
are  given  in  table  2.  The  average  set  of  the  Yellow  Newtown  for  three 
years  when  self -pollinated  was  about  12  per  cent,  as  contrasted  with 
the  normal  set  during  the  same  period  of  19.5  per  cent,  which  indicated 
the  variety  to  be  largely  self -fruitful.  This  agrees  with  the  work  of 
Lewis  and  Vincent  (1909)  in  Oregon.  The  work  of  Morris  (1921) 
in  Washington,  and  Vincent  (1920)  in  Idaho,  indicated  the  Newtown 
to  be  largely  self -unfruitful.  These  workers,  however,  simply  covered 
the  blossoms  and  did  not  actually  apply  the  pollen.  The  data  pre- 
viously presented  indicate  that  such  a  method  may  not  be  a  satisfactory 
one  for  determining  self-unfruitfulness. 


10 


UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION 


The  Yellow  Bellflower,  upon  the  basis  of  three  years'  work, 
appeared  to  be  a  satisfactory  pollinizer  for  the  Yellow  Newtown, 
giving  a  set  of  nearly  31  per  cent,  as  contrasted  with  the  normal  set 
of  19.5  per  cent.  While  Red  Pearmain  pollen  appeared  to  be  cross- 
compatible  upon  Yellow  Newtown  stigmas,  it  possessed  no  especial 

TABLE  2 
Yellow  Newtown  Hand-Pollination  Experiments    ( Watson ville) 


Pollen  variety 

Years 
inclusive 

Number 

flowers 

pollinated 

Per  cent 

set 

Per  cent 

normal 

set 

Per  cent 

pollen 

germinated 

Self-pollinated 

1919-21 
1919-21 
1920-21 
1920-21 

3390 

2797 

827 

1103 

MM 

12.22 
30.76 
12.81 
18.93 

19.56 
19.56 
14.41 
14.41 

70 

Yellow  Bellflower 

66 

Red  Pearmain 

65 

White  Winter  Pearmain 

75 

merit  as  a  pollinizer,  since  it  gave  a  percentage  of  set  less  than  the 
normal  set.  This  was  also  essentially  true  of  the  White  Winter 
Pearmain,  although  it  gave  a  somewhat  higher  set  than  normal  for 
the  two  years.  The  latter,  therefore,  may  be  considered  satisfactory 
as  a  pollinizer  of  the  Yellow  Newtown. 

Yellow  Bellflower — The  data  in  table  3  with  4328  self-pollinations 
again  show  the  Yellow  Bellflower  to  be  self -unfruitful.    Furthermore, 

TABLE  3 

Yellow  Bellflower  Pollination  Experiments   (Watsonville  and  Sebastopol) 


Pollen  variety 


Self-pollinated 

Yellow  Newtown 

Red  Pearmain 

White  Winter  Pearmain 

Gravenstein 

Jonathan 

Tompkins  King 

Esopus 

Rhode  Island  Greening . 
Delicious 


Years 
inclusive 


1919-23 
1919-23 
1920-21 
1920-21 
1922-23 

1922 
1922-23 
1922 
1922 
1923 


Number 

flowers 

pollinated 


4328 

4445 

1080 

1086 

899 

736 

883 

1037 

965 

163 


Per  cent 
set 


0.07 
4.29 
0.77 
0.85 
0.00 
0.08 
0.00 
0.00 
0.00 
3.00 


Per  cent 

normal 

set 


8.5 

8.5 

6.6 

6.6 

6.6 

11.4 

6.6 

11.4 

11.4 

1.9 


Per  cent 

pollen 

germinated 


74 
79 
67 
72 
25 
75 
22 
90 
40 
50 


the  only  pollen  which  appeared  to  give  a  set  greater  than  the  normal 
was  the  Delicious.  The  number  of  blossoms  employed  with  Delicious 
pollen,  however,  was  small  (163),  and  the  cross  was  made  only  one 
season.     In  addition,  while  the  set  with  Delicious  of  3.0  per  cent 


Bul.  426] 


APPLE   POLLINATION   STUDIES   IN    CALIFORNIA 


11 


seemingly  was  not  large,  the  normal  set  was  relatively  small,  1.9  per 
cent.  When  the  Yellow  Bellflower  was  cross-pollinated  with  Yellow 
Newtown  the  average  set  for  three  years  was  a  little  over  4.0  per  cent, 
as  contrasted  with  an  average  normal  set  of  8.5  per  cent  during  the 
same  period. 

The  Red  Pearmain  with  1080  crosses,  White  Winter  Pearmain 
with  1086  crosses,  Gravenstein  with  899  crosses,  and  Tompkins  King 
with  883  crosses  failed  during  two  seasons '  work  to  give  an  appreciable 
set  when  used  to  cross-pollinate  the  Yellow  Bellflower.  With  only  one 
season's  work,  the  Jonathan,  with  736  crosses,  the  Esopus  (Spitzen- 
burg),  with  1037  crosses,  and  the  Rhode  Island  Greening,  with  965 
crosses,  also  failed  to  result  in  any  set  of  Yellow  Bellflower  fruits. 
While  the  data  cannot  be  taken  as  showing  definite  cross-incompati- 
bility, they  suggest  this  to  be  true  in  the  case  of  Gravenstein,  Tomp- 
kins King,  Esopus,  and  Rhode  Island  Greening. 

The  pollen  germination  of  the  Gravenstein  and  the  Tompkins  King 
was  unsatisfactorily  low. 


TABLE  4 

Gravenstein  Pollination  Experiments   (Sebastopol) 


Pollen  variety 


Years 
inclusive 


Number 

flowers 

pollinated 


Per  cent 
set 


Per  cent 

normal 

set 


Per  cent 

pollen 

germinated 


Self -pollinated 

Esopus 

Delicious 

Jonathan 

Rhode  Island  Greening 

Yellow  Newtown 

Yellow  Bellflower 

Tompkins  King 

Baldwin 


1921-23 
1921-23 
1921-23 
1921-23 
1922-23 
1922-23 
1922-23 
1922-23 
1923 


3593 
2748 
3031 
2395 
1239 
1334 
1715 
1816 
890 


0.09 
2.60 
9.30 
2.34 
0.00 
6.20 
0.30 
0.00 
0.00 


6.75 
6.75 
6.75 
6.75 
6.63 
6.63 
6.63 
6.63 
9.10 


14 

81 
78 
72 
50 
73 
78 
30 
25 


Gravenstein. — The  data  in  table  4  show  as  the  result  of  three  years ' 
work  and  3593  self-pollinations,  that  the  Gravenstein  is  self -unfruitful. 
This  agrees  with  the  work  of  Lewis  and  Vincent  (1909)  in  Oregon; 
and  Powell  (1902)  in  Delaware.  Morris  (1921)  in  "Washington,  and 
Vincent  (1920)  in  Idaho,  however,  found  that  when  the  Gravenstein 
blossoms  were  bagged  and  not  actually  hand-pollinated,  the  percent- 
ages setting  fruit  were  5.1  and  3.5,  respectively. 

The  Delicious  proved  to  be  the  best  pollinizer  for  the  Gravenstein, 
during  three  years'  work  as  a  result  of  3031  crossings,  giving  an 
average  set  of  9.3  per  cent  as  contrasted  with  the  normal  set  of  6.75 


12 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


per  cent.  Morris  (1921)  crossed  99  Gravenstein  blossoms  with  Deli- 
cious pollen  and  found  16  per  cent  of  the  blossoms  set  fruit.  Another 
satisfactory  pollinizer  was  the  Yellow  Newtown,  giving  a  set  com- 
parable with  the  normal  set.  Morris  (1921),  crossing  34  Gravenstein' 
blossoms  with  Jonathan  pollen,  found  that  about  18  per  cent  set  fruit, 
but  crossing  57  Gravenstein  blossoms  with  Esopus  found  that  none  of 
them  set  fruit.  Vincent  (1915)  also  found  the  Jonathan  was  cross- 
fruitful  upon  the  Gravenstein. 

The  Rhode  Island  Greening,  Yellow  Bellflower,  Tompkins  King, 
and  Baldwin  appeared  to  be  cross-incompatible  with  Gravenstein. 

The  Gravenstein  did  not  produce  abundant  pollen,  which,  more- 
over, lacked  viability,  as  is  shown  by  the  low  average  germination 
percentage  of  14.0.  It  appears  that  the  self-unfruitfulness  and  the 
cross-incompatibility  with  other  varieties  may  be  due  in  part  to  this. 
With  the  pollen  of  the  Tompkins  King  and  the  Baldwin  used  in  cross- 
pollinating  the  Gravenstein,  the  germination  was  also  unsatisfactorily 
low,  being  30.0  and  25  per  cent,  respectively. 

White  Winter  Pearmain. — The  two  years'  data  in  table  5  show  the 
White  Winter  Pearmain  to  be  self-unfruitful.  This  agrees  with  the 
work  of  Auchter  (1922),  Morris  (1921),  and  Vincent  (1920).  The 
best  pollinizer  of  the  White  Winter  Pearmain  seemed  to  be  the  Red 
Pearmain,  although  the  set  resulting  was  about  one-half  that  of  the 
normal  set.  The  Yellow  Bellflower  and  the  Yellow  Newtown,  when 
used  as  pollinizers,  were  both  inter-fruitful  with  the  White  Winter 
Pearmain. 

TABLE  5 

White  Winter  Pearmain  Pollination  Experiments  ( Watson ville) 


Pollen  variety 

Years 
inclusive 

Number 

flowers 

pollinated 

Per  cent 
set 

Per  cent 

normal 

set 

Per  cent. 

pollen 

germinated 

Self-pollinated 

1920-21 
1920-21 
1920-21 
1920-21 

940 

771 

943 

1479 

0.00 
2.12 
1.71 
5.58 

11.32 
11.32 
11.32 
11.32 

72 

Yellow  Bellflower 

71 

Yellow  Newtown 

78 

Red  Pearmain 

63 

Tompkins  King. — The  data  from  two  years'  work,  as  shown  in 
table  6,  indicate  that  the  Tompkins  King  is  self -unfruitful,  as  reported 
by  Lewis  and  Vincent  (1909),  and  Morris  (1921).  Auchter,  how- 
ever, employing  blossoms  covered  but  not  actually  hand-pollinated, 
reported  that  in  Maryland  the  Tompkins  King  was  self -fruitful.  The 
germination  tests  indicated  a  somewhat  low  viability  of  the  Tompkins 


Bul.  426] 


APPLE    POLLINATION    STUDIES   IN    CALIFORNIA 


13 


King  pollen  and  markedly  low  viability  or  imperfect  pollen  for  the 
Gravenstein.  The  Jonathan,  of  the  varieties  tested,  appeared  to  be 
the  best  pollinizer  for  the  Tompkins  King. 


TABLE  6 

Tompkins  King  Pollination  Experiments  (Sebastopol) 


Pollen  variety 


Years 
inclusive 

Number 

flowers 

pollinated 

Per  cent 

set 

Per  cent 
normal 

set 

1922-23 

1990 

0 

27.6 

1922-23 

1349 

0 

27.6 

1922-23 

853 

0 

27.6 

1922-23 

1411 

1.7 

27.6 

1922-23 

1072 

14.1 

27.6 

1923 

359 

0 

18.9 

Per  cent 

pollen 

germinated 


Self-pollinated 

Gravenstein 

Rhode  Island  Greening 

Yellow  Bellflower 

Jonathan 

Yellow  Newtown 


30 

8 
67 
78 
73 
70 


Bed  Pearmain. — The  data  in  table  7  indicate  that  the  Red  Pear- 
main  is  self-unfruitful,  and  that  the  pollen  of  Yellow  Bellflower, 
Yellow  Newtown,  and  White  Winter  Pearmain  is  cross-compatible  with 
the  stigmas  of  Red  Pearmain.  While  the  sets  of  Red  Pearmain 
pollinated  with  Yellow  Bellflower  and  Yellow  Newtown  were  less  than 
the  normal  set,  that  resulting  from  White  Winter  Pearmain  pollen 
was  in  excess  of  the  normal  set. 


TABLE  7 
Red  Pearmain  Pollination  Experiments  ( Watson ville) 


Pollen  variety 

Years 
inclusive 

Number 

flowers 

pollinated 

Per  cent 

set 

Per  cent 
normal 

set 

Per  cent 

pollen 

germinated 

Self-pollinated 

1920-21 

1920-21 

1920-21 

1921 

306 
893 
890 
676 

0.19 
3.57 
2.65 

8.89 

7.16 
7.16 
7.16 

7.22 

63 

Yellow  Bellflower 

70 

Yellow  Newtown . .. 

67 

White  Winter  Pearmain 

74 

Esopus  {Spitzenburg) . — The  data  of  three  years  in  table  8  indicate 
that  the  Esopus  (Spitzenburg)  is  partially  self -fruitful.  This  agrees 
with  the  work  of  Lewis  and  Vincent  (1909).  Morris  (1921)  and 
Waugh  (1898)  likewise  obtained  data  which  showed  a  tendency  for  the 
variety  to  be  self -fruitful.  Vincent  (1920)  and  Waite  (1899),  how- 
ever, appeared  to  find  it  self -unfruitful  under  Idaho  and  New  York 
conditions,  respectively.  The  pollen  of  Gravenstein,  as  a  result  of  three 
seasons'  work,  was  shown  to  be  cross-incompatible  upon  Esopus 
(Spitzenburg)  stigmas.   The  Gravenstein  pollen,  however,  gave  a  low 


14 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


germination  test.  Both  the  Jonathan  and  the  Delicious  pollen  gave 
exceptionally  high  sets,  55.5  and  36.4  per  cent,  respectively,  as  con- 
trasted with  the  normal  set  of  11.3.  Lewis  and  Vincent  found  the 
pollen  of  Jonathan  to  be  highly  compatible  upon  the  stigmas  of  Esopus 
(Spitzenburg)  and  Morris  found  this  was  true  for  both  Jonathan  and 
Delicious  pollen  upon  Esopus  (Spitzenburg)  stigmas. 

TABLE  8 
Esopus  (Spitzenburg)  Pollination  Experiments  (Sebastopol) 


Pollen  variety 

Years 
inclusive 

Number 

flowers 

pollinated 

Per  cent 

set 

Per  cent 
normal 

set 

Per  cent 

pollen 

germinated 

Self -pollinated 

1921-23 

1921-23 

1921 

1921 

1037 

1004 

632 

730 

4.4 

0.1 

55.5 

36.4 

20.5 
20.5 
11.3 
11.3 

85 

Gravenstein 

12 

Jonathan 

70 

Delicious..                   

85 

Additional  Varieties. — The  Rhode  Island  Greening,  Jonathan, 
Delicious,  and  Baldwin  were  in  each  case  self-pollinated  and  cross- 
pollinated  with  Gravenstein.  The  data  are  given  in  table  9.  The  work 
of  two  years  with  Rhode  Island  Greening,  Jonathan,  and  Delicious 
indicate  that  these  varieties  are  self -unfruitful. 

The  data  obtained  with  the  Delicious  agree  with  the  work  of 
Vincent  (1920),  Morris  (1921),  and  Crandall  (1922).  The  data  with 
the  Jonathan  agree  with  the  findings  of  Lewis  and  Vincent  in  Oregon 
and  Morris  in  Washington.  Vincent  in  Idaho,  and  Wicks  (1918)  in 
Arkansas,  however,  seemed  to  find  the  Jonathan  partly  self-fruitful. 
Crandall  (1922),  Gowan  (1920),  Lewis  and  Vincent  (1909),  Vincent 


TABLE  9 

Additional  Pollination  Experiments 


Variety  pollinated 

Pollen  variety 

Years 
inclusive 

Number 
flowers 
polli- 
nated 

Per  cent 
set 

Percent 
normal 

set 

Per  cent 
pollen 
germi- 
nated 

Rhode  Island  Greening 

Rhode  Island  Greening 

Jonathan 

Self-pollinated.. 

Gravenstein 

Self-pollinated.. 

Gravenstein 

Self-pollinated.. 

Gravenstein 

Self-pollinated.. 
Gravenstein 

1922-23 

1922-23 

1921-23 

1922-23 

1922-23 

1922 

1923 

1923 

582 
449 
600 
461 
426 
150 
209 
99 

0 

0 

0.4 

0 

0 

0 

7.1 

0 

9.8 
9.8 
28.4 
28.4 
22.0 
9.1 
19.8 
19.8 

43 
12 
70 

Jonathan 

12 

Delicious 

57 

Delicious 

15 

Baldwin 

15 

Baldwin 

10 

BUL.  426]  APPLE   POLLINATION   STUDIES   IN    CALIFORNIA  15 

(1920),  Waite  (1899),  Waugh  (1898),  and  Sax  (1922)  found  the 
Rhode  Island  to  be  self -unfruitful,  although  Morris  found  it  partially 
self-fruitful. 

The  data  in  table  9  indicate  that  the  Baldwin  is  self -fruitful.  This 
agrees  with  the  work  of  Gowen,  and  Lewis  and  Vincent.  Morris, 
Auchter  (1922)  and  MacDaniels  (1926)  also  found  the  Baldwin  partly 
self-fruitful.  Waugh  and  Sax,  however,  found  the  Baldwin  self- 
unfruitful,  although  Waugh  simply  bagged  the  blossoms  without 
actually  applying  the  pollen. 

The  pollen  of  Gravenstein  appeared  to  be  cross-incompatible  with 
each  of  the  four  varieties.  The  Gravenstein  pollen  viability  was  low, 
although  this  was  also  true  of  the  Baldwin  pollen,  which  gave  a  set 
upon  Baldwin  stigmas  of  about  7  per  cent. 


SUMMARY 

1.  The  use  of  bees  as  a  means  of  effecting  pollination  in  an  apple 
orchard  greatly  increased  the  set  of  fruit  when  contrasted  with  the 
normal  set. 

2.  Cross-pollination  increased  the  set  of  fruit,  even  with  a  self- 
fruitful  variety  like  the  Yellow  Newtown. 

3.  The  actual  application  of  the  pollen  by  insects  or  by  hand 
seemed  necessary  to  insure  pollination  of  Yellow  Newtown  and  Yellow 
Bellflower  blossoms. 

4.  In  the  case  of  these  two  varieties,  the  method  of  bagging  or 
enclosing  unemasculated  blossoms  with  mosquito-bar  to  determine  self- 
compatibility  or  self -incompatibility  seemed  unreliable. 

5.  It  seemed  advisable  to  enclose  emasculated  Yellow  Newtown  or 
Yellow  Bellflower  blossoms  in  paper  sacks  in  order  to  lessen  the 
drying  out  of  the  wounded  floral  parts  remaining  and  to  prolong  the 
period  of  receptivity.  There  was  no  evidence,  however,  to  indicate 
the  advisability  of  bagging  to  exclude  chance  pollination  of  emascu- 
lated flowers. 

6.  Under  the  conditions  of  the  experiment,  the  Yellow  Newtown, 
Esopus   (Spitzenburg),  and  Baldwin  were  self -fruitful. 

7.  The  Yellow  Bellflower,  Gravenstein,  White  Winter  Pearmain, 
Tompkins  King,  Rhode  Island  Greening,  Delicious,  Red  Pearmain,  and 
Jonathan  were  considered  self -unfruitful. 

8.  The  Gravenstein  did  not  satisfactorily  cross-pollinate  any  of  the 
varieties  tested.  This  appeared  to  be  the  result  of  defective  and 
non-viable  pollen,  as  determined  by  germination  tests  and  by  micro- 
scopic examination  of  the  pollen  grains. 


16  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

9.  The  pollen  of  Tompkins  King,  Esopus,  and  Rhode  Island 
Greening  upon  the  stigmas  of  the  Yellow  Bellnower ;  of  Rhode  Island 
Greening,  Thompkins  King,  and  Baldwin  upon  the  Gravenstein;  and 
of  Rhode  Island  Greening  and  Yellow  Newtown  upon  the  stigmas  of 
Tompkins  King,  did  not  result  in  satisfactory  sets  of  fruits. 

10.  The  Yellow  Bellnower,  Red  Pearmain,  and  the  White  Winter 
Pearmain  were  considered  good  varieties  for  pollinating  the  Yellow 
Newtown ;  the  Yellow  Newtown  and  Delicious  for  the  Yellow  Bellnower 
and  for  the  Gravenstein;  the  Red  Pearmain  for  the  White  Winter 
Pearmain ;  the  Jonathan  for  the  Tompkins  King ;  the  White  Winter 
Pearmain  for  the  Red  Pearmain ;  and  the  Jonathan  and  Delicious  for 
the  Esopus  (Spitzenburg). 

11.  The  pollen  of  certain  varieties  was  considered  as  partially 
cross-compatible  upon  the  stigmas  of  certain  flowers  but  not  suffi- 
ciently so  for  the  cross-pollination  of  commercial  plantings.  This  was 
true  of  Esopus  and  Jonathan  pollen  upon  the  stigmas  of  Gravenstein ; 
the  Yellow  Bellnower  and  Yellow  Newtown  upon  White  Winter 
Pearmain;  the  Yellow  Bellnower  upon  Tompkins  King;  and  Yellow 
Bellflower  and  Yellow  Newtown  pollen  upon  Red  Pearmain  stigmas. 

Acknowledgments :  The  writer  wishes  to  express  appreciation  for 
help  received  in  the  field  from  certain  graduate  students  as  follows: 
E.  S.  Yocco,  H.  E.  Jacob,  L.  P.  Latimer  and  R.  H.  Rawl. 


LITERATURE  CITED 

Alderman,  W.  H. 

1918.  Experimental  work  on  self-sterility  of  the  apple.  Proc.  Amer.  Soc. 
Hort.  Sci.  14:  94-101   (1917). 

AUCHTER,  E.   O. 

1922.     Apple  pollen  and  pollination  studies  in  Maryland.     Proc.  Amer.  Soc. 
Hort.  Sci.  18:  51-80'  (1921). 
Crandall,  C.  S. 

1922.     Eesults  from  self-pollination  of  apple  flowers.    Proc.  Amer.  Soc.  Hort. 
Sci.  18:  95-100  (1921). 
Ewert,  E. 

1906.  Blutenbiologie  und  Tragbarkeit  unserer  Obstbaume.     Landw.  Jahrb. 

35:  259-287. 

1907.  Die  Parthenocarpie  oder  Jungfernfriichtigkeit  der  Obstbaume.    Paul 

Parey,  Berlin.     58  p. 

1909.  Neuere  Untersuchungen  iiber  Parthenokarpie  bei  Obstbaumen  und 
einigen  anderen  fruchttragenden  Gewachsen.  Landw.  Jahrb.  38: 
767-839. 


BUL.426]  APPLE   POLLINATION   STUDIES   IN    CALIFORNIA  17 

GOWAN,  J.  W. 

1920.  Self-sterility  and  cross-sterility  in  the  apple.     Maine  Agr.  Exp.  Sta. 

Bui.  287:  61-88. 
Heincke,  A.  J. 

1917.  Factors  influencing  the  abscission  of  flowers  and  partially  developed 

fruits  of  the  apple    (Pyrus  malus  L.)   Cornell  Agr.  Exp.  Sta.  Bui. 
393:  43-112. 
Hendrickson,  A.  H. 

1916.     The  common  honey  bee  as  an  agent  in  prune  pollination.     California 
Agr.  Exp.  Sta.  Bui.  274:   126-132. 
Hooper,  C.  H. 

1913.     The    pollination    of   fruit   trees    and   its   bearing    on    planting.      Gard. 
Chron.  3  ser.  54:   393-394,  420. 
Lewis,  C.  I.,  and  C.  C.  Vincent 

1909.     Pollination  of  the  apple.     Oregon  Agr.  Exp.  Sta.  Bui.  104:  3-40. 
MacDaniels,  L.  H. 

1926.     Pollination  studies  with  certain  New  York  state  apple  varieties.     Proc. 
Amer.  Soc.  Hort.  Sci.  22:  87-96   (1925). 
Morris,  O.  M. 

1921.  Studies  in  apple  pollination.     Washington  Agr.  Exp.  Sta.  Bui.  163: 

1-32. 
Powell,  G.  H. 

1902.     The  pollination  of  apples.    Delaware  Agr.  Exp.  Sta.  Ept.  13:  112-116. 
Sax,  K. 

1922.  Sterility   relationship   in    Maine   apple   varieties.      Maine   Agr.   Exp. 

Sta.  Bui.  307:  61-76. 
Tufts,  W.  P.,  and  Guy  L.  Philp 

1923.  Pear  pollination.     California  Agr.   Exp.   Sta.   Bui.   373:    1-36. 
Vincent,  C.  C. 

1915.     Report  of  the  department  of  horticulture.     Idaho  Agr.  Exp.  Sta.  Bui. 
84:   1-23. 

1920.     Results  of  pollination  studies  at  Idaho  university.     Better  Fruit  14: 
No.  8:   11-15. 
Waite,  M.  B. 
1899.     Pollination    of    pomaceous    fruits.      U.S.    Dept.    Agr.    Yearbook.    1898: 
167-180. 
Waugh,  F.  A. 

1898.     Proc.  Amer.  Pomol.  Soc.  25:   86-94. 
Wicks,  W.  H. 

1918.  The  effect  of  cross-pollination  on  the  size,  color,  shape,  and  quality 

of  the  apple.    Arkansas  Agr.  Exp.  Sta.  Tech.  Bui.  143:  1-48. 


STATION  PUBLICATIONS  AVAILABLE   FOR  FREE   DISTRIBUTION 


BULLETINS 


No. 

253.  Irrigation   and  Soil  Conditions  in  the 
Sierra   Nevada   Foothills,   California. 

261.  Melaxuma    of    the    Walnut,     "Juglans 

regia." 

262.  Citrus  Diseases  of  Florida   and  Cuba 

Compared  with  Those  of  California. 

263.  Size  Grades  for  Ripe  Olives. 

268.  Growing  and  Grafting  Olive  Seedlings. 
273.  Preliminary  Report  on  Kearney  Vine- 
yard  Experimental   Drain. 

275.  The     Cultivation     of     Belladonna     in 

California. 

276.  The  Pomegranate. 

277.  Sudan   Grass. 

278.  Grain    Sorghums. 

279.  Irrigation  of  Rice  in   California. 
283.  The  Olive  Insects  of  California. 
294.  Bean   Culture  in   California. 

304.  A  Study  of  the  Effects  of  Freezes  on 

Citrus    in    California. 
310.   Plum    Pollination. 

312.  Mariout  Barley. 

313.  Pruning      Young      Deciduous      Fruit 

Trees. 
319.   Caprifigs    and    Caprification. 

324.  Storage  of  Perishable  Fruit  at  Freez- 

ing Temperatures. 

325.  Rice     Irrigation     Measurements     and 

Experiments   in    Sacramento   Valley, 

1914-1919. 
328.  Prune   Growing  in   California. 
331.   Phylloxera-Resistant    Stocks. 
335.   Cocoanut    Meal    as    a    Feed   for   Dairy 

Cows  and   Other  Livestock. 

339.  The    Relative    Cost    of    Making    Logs 

from   Small  and  Large  Timber. 

340.  Control     of     the     Pocket     Gopher     in 

California. 

343.  Cheese    Pests    and    Their    Control. 

344.  Cold   Storage   as   an   Aid   to   the   Mar- 

keting of  Plums. 

346.  Almond    Pollination. 

347.  The  Control  of  Red  Spiders  in  Decid- 

uous Orchards. 

348.  Pruning  Young  Olive  Trees. 

349.  A    Study    of    Sidedraft    and    Tractor 

Hitches. 

350.  Agriculture      in      Cut-over      Redwood 

Lands. 

352.  Further  Experiments  in  Plum  Pollina- 

tion. 

353.  Bovine   Infectious   Abortion. 

354.  Results  of  Rice  Experiments  in   1922. 

357.  A    Self-mixing    Dusting    Machine    for 

Applying      Dry      Insecticides      and 
Fungicides. 

358.  Black    Measles,    Water    Berries,     and 

Related  Vine  Troubles. 

361.  Preliminary    Yield    Tables    for    Second 

Growth   Redwood. 

362.  Dust  and  the  Tractor  Engine. 

363.  The  Pruning  of  Citrus  Trees  in  Cali- 

fornia. 

364.  Fungicidal    Dusts    for   the   Control   of 

Bunt. 

365.  Avocado  Culture  in  California. 

366.  Turkish  Tobacco  Culture,   Curing  and 

Marketing. 

367.  Methods  of  Harvesting  and  Irrigation 

in   Relation  of  Mouldy  Walnuts. 

368.  Bacterial  Decomposition  of  Olives  dur- 

ing Pickling. 

369.  Comparison     of     Woods     for     Butter 

Boxes. 


No. 

370. 

371. 

372. 

373. 
374. 


375. 

376. 

377. 
379. 
380. 

381. 

382. 

383. 

385. 
386. 

387. 
388. 

389. 
390. 

391. 

392. 
393. 
394. 

395. 
896. 

397. 

398. 
399. 


400. 
401. 

402. 
403. 
404. 
405. 
406. 
407. 


408. 
409. 


410. 
411. 
412. 

413. 
414. 


Browning  of  Yellow  Newtown  Apples. 

The  Relative  Cost  of  Yarding  Small 
and   Large  Timber. 

The  Cost  of  Producing  Market  Milk  and 
Butterfat  on  246  California  Dairies. 

Pear   Pollination. 

A  Survey  of  Orchard  Practices  in  the 
Citrus  Industry  of  Southern  Cali- 
fornia. 

Results  of  Rice  Experiments  at  Cor- 
tena,    1923. 

Sun-Drying  and  Dehydration  of  Wal- 
nuts. 

The  Cold   Storage  of  Pears. 

Walnut   Culture   in   California. 

Growth  of  Eucalyptus  in  California 
Plantations. 

Growing  and  Handling  Asparagus 
Crowns. 

Pumping  for  Drainage  in  the  San 
Joaquin    Valley,    California. 

Monilia  Blossom  Blight  (Brown  Rot) 
of  Apricot. 

Pollination   of   the    Sweet   Cherry. 

Pruning  Bearing  Deciduous  Fruit 
Trees. 

Fig  Smut. 

The  Principles  and  Practice  of  Sun- 
drying  Fruit. 

Berseem  or  Egyptian   Clover. 

Harvesting  and  Packing  Grapes  in 
California. 

Machines  for  Coating  Seed  Wheat  with 
Copper   Carbonate   Dust. 

Fruit    Juice    Concentrates. 

Crop  Sequences  at  Davis. 

Cereal  Hay  Production  in  California. 
Feeding  Trials  with  Cereal  Hay. 

Bark  Diseases  of  Citrus  Trees. 

The  Mat  Bean  (Phaseolus  aconitifo- 
lius). 

Manufacture  of  Roquefort  Type  Cheese 
from   Goat's  Milk. 

Orchard  Heating  in  California. 

The  Blackberry  Mite,  the  Cause  of 
Redberry  Disease  of  the  Himalaya 
Blackberry,    and   its   Control. 

The  Utilization  of  Surplus  Plums. 

Cost  of  Work  Horses  on  California 
Farms. 

The  Codling  Moth  in  Walnuts. 

Farm-Accounting  Associations. 

The  Dehydration  of  Prunes. 

Citrus  Culture  in  Central  California. 

Stationary  Spray  Plants  in  California. 

Yield,  Stand  and  Volume  Tables  for 
White  Fir  in  the  California  Pine 
Region. 

Alternaria  Rot  of  Lemons. 

The  Digestibility  of  Certain  Fruit  By- 
products as  Determined  for  Rumi- 
nants. 

Factors  Affecting  the  Quality  of  Fresh 
Asparagus  after  it  is  Harvested. 

Paradichlorobenzene  as  a  Soil  Fumi- 
gant. 

A  Study  of  the  Relative  Values  of  Cer- 
tain Root  Crops  and  Salmon  Oil  as 
Sources  of  Vitamin  A  for  Poultry. 

The  California  Poultry  Industry;  a 
Statistical  Study. 

Planting  and  Thinning  Distances  for 
Deciduous  Fruit  Trees. 


No. 

87.  Alfalfa. 
117.  The    Selection    and    Cost    of    a    Small 

Pumping  Plant. 
127.  House    Fumigation. 
129.  The  Control  of  Citrus  Insects. 
136.  Melilotus    indica    as    a    Green-Manure 

Crop  for  California. 
144.  Oidium    or    Powdery    Mildew    of    the 

Vine. 
157.   Control  of  the  Pear  Scab. 
160.   Lettuce  Growing  in  California. 
164.   Small  Fruit  Culture  in  California. 
166.  The   County  Farm  Bureau. 
170.   Fertilizing     California     Soils     for     the 

1918   Crop. 
173.  The    Construction    of   the   Wood-Hoop 

Silo. 

178.  The   Packing  of  Apples  in   California. 

179.  Factors    of    Importance    in    Producing 

Milk  of  Low  Bacterial  Count. 
190.  Agriculture  Clubs  in  California. 
199.   Onion    Growing   in    California. 

202.  County   Organizations   for   Rural   Fire 

Control. 

203.  Peat   as   a   Manure   Substitute. 

209.  The  Function  of  the  Farm  Bureau. 

210.  Suggestions  to  the  Settler  in  California. 
212.   Salvaging    Rain-Damaged    Prunes. 
215.   Feeding  Dairy  Cows  in  California. 
217.  Methods   for   Marketing  Vegetables   in 

California. 
220.   Unfermented   Fruit  Juices. 
228.  Vineyard  Irrigation  in  Arid  Climates. 

230.  Testing  Milk,    Cream,    and   Skim   Milk 

for  Butterfat. 

231.  The    Home    Vineyard. 

232.  Harvesting    and    Handling    California 

Cherries    for    Eastern    Shipment. 

234.  Winter  Injury  to  Young  Walnut  Trees 

during  1921-22. 

235.  Soil     Analysis     and     Soil     and     Plant 

Inter-relations. 

236.  The    Common     Hawks     and    Owls    of 

California    from    the    Standpoint    of 
the  Rancher. 

237.  Directions  for  the  Tanning  and  Dress- 

ing of  Furs. 

238.  The  Apricot  in  California. 

239.  Harvesting     and     Handling     Apricots 

and  Plums  for  Eastern  Shipment. 

240.  Harvesting    and    Handling    Pears    for 

Eastern   Shipment. 

241.  Harvesting  and  Handling  Peaches  for 

Eastern    Shipment. 

243.  Marmalade  Juice  and  Jelly  Juice  from 

Citrus  Fruits. 

244.  Central  Wire  Bracing  for  Fruit  Trees. 

245.  Vine   Pruning  Systems. 

247.  Colonization    and    Rural   Development. 

248.  Some    Common    Errors    in   Vine  Prun- 

ing and  Their  Remedies. 

249.  Replacing    Missing    Vines. 

250.  Measurement   of   Irrigation   Water   on 

the  Farm. 

252.  Supports  for  Vines. 

253.  Vineyard  Plans. 

254.  The  Use  of  Artificial  Light  to  Increase 

Winter    Egg    Production. 


CIRCULARS 
No. 
255. 


256. 
257. 
258. 
259. 
261. 
262. 
263. 
264. 

265. 
266. 

267. 


270. 
272. 

273. 
274. 

276. 
277. 

278. 

279. 

281. 

282. 

283. 

284. 
285. 
286. 
287. 
288. 
289. 
290. 
291. 

292. 
293. 
294. 
295. 

296. 

298. 

299. 
300. 
301. 
302. 
303. 

304. 
305. 
306. 

307. 
308, 


Leguminous  Plants  as  Organic  Fertil- 
izer   in    California    Agriculture. 

The   Control   of  Wild   Morning   Glory. 

The  Small-Seeded  Horse  Bean. 

Thinning   Deciduous   Fruits. 

Pear  By-products. 

Sewing  Grain  Sacks. 

Cabbage  Growing  in  California. 

Tomato  Production  in  California. 

Preliminary  Essentials  to  Bovine 
Tuberculosis  Control. 

Plant   Disease   and   Pest   Control. 

Analyzing  the  Citrus  Orchard  by 
Means   of    Simple   Tree   Records. 

The  Tendency  of  Tractors  to  Rise  in 
Front;    Causes   and  Remedies. 

An   Orchard  Brush  Burner. 

A  Farm  Septic  Tank. 

California  Farm  Tenancy  and  Methods 
of  Leasing. 

Saving  the  Gophered   Citrus  Tree. 

Fusarium  Wilt  of  Tomato  and  its  Con- 


by  Mean 
Cannini 


Home   Canning. 

Head,  Cane,  and  Cordon  Pruning  of 
Vines. 

Olive  Pickling  in  Mediterranean  Coun- 
tries. 

The  Preparation  and  Refining  of  Olive 
Oil   in    Southern   Europe. 

The  Results  of  a  Survey  to  Determine 
the  Cost  of  Producing  Beef  in  Cali- 
fornia. 

Prevention  of  Insect  Attack  on  Stored 
Grain. 

Fertilizing  Citrus  Trees  in  California. 

The  Almond   in   California. 

Sweet  Potato  Production  in  California. 

Milk  Houses  for  California  Dairies. 

Potato   Production   in   California. 

Phylloxera  Resistant  Vineyards. 

Oak  Fungus  in  Orchard  Trees. 

The  Tangier  Pea. 

Blackhead  and  Other  Causes  of  Loss 
of  Turkeys  in  California. 

Alkali   Soils. 

The    Basis    of   Grape    Standardization. 

Propagation    of   Deciduous   Fruits. 

The  Growing  and  Handling  of  Head 
Lettuce  in   California. 

Control  of  the  California  Ground 
Squirrel. 

The  Possibilities  and  Limitations  of 
Cooperative  Marketing. 

Poultry   Breeding  Records. 

Coccidiosis  of  Chickens. 

Buckeye  Poisoning  of  the  Honey  Bee. 

The   Sugar  Beet  in   California. 

A  Promising  Remedy  for  Black  Measles 
of  the  Vine. 

Drainage  on  the  Farm. 

Liming  the  Soil. 

A  General  Purpose  Soil  Auger  and  its 
Use  on  the  Farm. 

American   Foulbrood   and  its   Control. 

Cantaloupe  Production  in  California. 


The  publications  listed  above  may  be  had  by  addressing 

College  of  Agriculture] 

University  of  California, 

Berkeley,  California. 


13m-5,'27 


